Additive manufacturing techniques are increasingly being used to produce medical devices, as such techniques typically enable the production of components having both porous portions (e.g., in regions where tissue in-growth is desired) and solid portions (e.g., in regions where greater structural strength is needed). Although additive manufacturing has significant advantages, such as enabling the porous sections to be manufactured with porosities and pore sizes tailored to a particular application, these techniques are not without their challenges. For example, while laser additive manufacturing techniques can typically produce much finer pores as compared to electron beam techniques, both approaches generally have difficulty in producing interconnecting pores that are smaller than a threshold size. This threshold size partially depends upon the size of the powder used as a raw material (typically in the range of 40 microns to 100 microns), and partially depends upon the size of the melt pool generated by the beam (typically in the range of 25 microns to 100 microns, depending on beam power, spot size, and scan speed).
In addition, smaller pores may trap fine powder which can be difficult to remove during the cleaning process. Although these smaller pores may be unsuitable for tissue in-growth, they may be suitable to partially infiltrate polymeric compositions to produce components for musculoskeletal articulating and non-articulating surfaces. When polymeric compositions are infiltrated in larger pores, there is a risk of the polymeric composition infiltrating through the entire thickness of the porous part, thereby clogging the pores that are typically provided to promote tissue in-growth. Another challenge associated with additive manufacturing is the time it takes to produce the porous components, as the computing and printing time can be significantly larger for structures with smaller pores than for those with larger pores.
Certain existing approaches have attempted to overcome these challenges by tailoring parameters of the additive manufacturing process itself. For example, certain approaches to preventing undesired infiltration of polymeric compositions include providing a thicker cross-section of the metallic portions of the manufactured product, or creating a gradient in the pore sizes. However, these approaches can produce additional challenges, such as those associated with providing tissue-conserving devices where minimal amount of metal and polyethylene is required, or where a thicker cross-section of polyethylene is required. One current approach to reducing the printing time is to increase the beam power and scan speed, such that a thicker layer is built on each pass. However, this approach comes with the challenge of increasing the size of the melt pool, and thus may further reduce the ability to produce finer pores. For these reasons among others, a need remains for further improvements in this technological field.